This invention relates to an axial displacement mechanism, and more specifically to a axial displacement mechanism specifically adapted for a turret table for use in machinery for the automated manufacture of tin boxes.
Although the following description is provided with exclusive reference to such machinery, it is to be mentioned that the axial displacement mechanism described could easily be applied to any surface which is required to be precisely orientated and disposed with respect to a tool or the like which works on a body or collects such a body from said surface, the precision being required to ensure faultless operation of the tool.
Automated tin box manufacture is accomplished by juxtaposing several different pieces of machinery and providing transfer means therebetween. Tin boxes can be manufactured in a vast number of different shapes and sizes and accordingly a single piece of machinery is required to be sufficiently versatile to enable manufacture of tin boxes in a large number of said shapes and sizes. It will be understood by those skilled in the art that the machinery used has a number of different components which can be exchanged to facilitate the manufacture of different boxes and currently the length of time taken to exchange all these various components to enable a particular set of machines to manufacture a different box shape can be up to an entire day. The invention hereinafter set forth, and also set forth in our co-pending applications have as their object the reduction of this time. Any reduction achievable in the xe2x80x9cchangeoverxe2x80x9d time is especially desirable when it is considered that tin box production rates using the machinery described hereinafter may reach 40 per minute.
Tin boxes can contain a wide variety of different goods, such as bottles, chocolates, biscuits, tea, coffee and the like. Manufacturers of such products commonly consider the containment of their product in tins because of the rigidity and durability which the sheet steel, from which such tins are commonly made, provides. Additionally, the containment of a product in a tin box may also suggest that the product therein is of a certain quality, especially as ornate and detailed print effects can be obtained on the surface of the metal plates from which the tin boxes are manufactured. Such effects cannot be achieved, or are achieved only to a much lesser degree by the containment of products in cardboard cartons or receptacles of plastics materials. A tin box in which such a product is contained has the further advantage of being reusable to contain other household items such as screws, nuts bolts, pencils and pens, etc. after the product originally contained therein has been consumed or otherwise utilised.
The various separate machines required in the manufacture of tin boxes are an xe2x80x9cAutomatic Curling Notching and Beadingxe2x80x9d machine, a xe2x80x9cbodymakerxe2x80x9d, a xe2x80x9cround and irregular seamerxe2x80x9d, and an xe2x80x9cend feederxe2x80x9d, each of which has a specific task to perform during the process of tin box manufacture. Each of these is now described.
The first stage in the process of automated tin box manufacture is the profiling of a simple sheet steel, and generally rectangular, blank from which the walls of the tin box are ultimately constituted. The blank is fed through an xe2x80x9cAutomatic Notching, Curling and Beadingxe2x80x9d machine, referred to hereinafter as an ANCB machine. This machine consists of a plurality of consecutively driven rollers disposed both above and below the blank as it passes therebetween, each of said rollers performing a forming step on the blank. The particular profile of each blank as it exits the ANCB machine depends on the ultimate shape of the tin, but in general the blank is substantially flat with the exception of a hem provided parallel with one of the longer edges of the blank and proximate thereto, a bead is provided on one of said longer edges, a partial curl is provided around the alternate longer edge, and a pair of hooks oppositely disposed with respect to one another on the shorter edges. Additionally, the ANCB machine has cutting means which notch the corners of the blank to preclude any interference effects which may be caused by said corners either when the blank is profiled and provided with the hooks along its shorter edges, when it is formed into the cross-sectional shape of the tin box, or when wrapped around and attached to the base of said tin box.
The hem provides a surface behind which the beaded lip of a tin lid can engage to inhibit the removal of a lid separately formed and applied around the uppermost edge of the tin box, the bead is provided to hide the sharp longer edge of the blank which ultimately forms said uppermost edge of the tin box, the partial curl on the alternate longer edge of the blank is provided to facilitate the attachment of the blank, after same has been formed into the desired cross-sectional shape, to the base of the tin box, and the hooks provided along the shorter edges of the blank facilitate the connection of said edges to one another after the forming operation.
The profiled blank is then fed from the ANCB machine into a bodymaker by a feed mechanism which generally comprises a pair of reciprocating feed bars whose motion is best described as being that of a xe2x80x9cwalking beamxe2x80x9d in conjunction with xe2x80x9cdisappearing guidesxe2x80x9d which simultaneously urge the profiled blank towards and over a forming mandrel and precisely align said blank thereon. The disappearing guides are rotated away from the blank when it is held in contact with the uppermost portion of the mandrel, which is generally of similar shape to the desired cross-sectional shape of the tin box to be manufactured, by a mandrel clamping arrangement. The removal of the disappearing guides (so-called because they are retracted and seem to xe2x80x9cdisappearxe2x80x9d within the machine during the forming of the blank around the mandrel) allows a pair of forming wings pivotally connected together and disposed above the mandrel to rotate about their pivot and form said blank, which is at this stage still substantially planar, around the said mandrel. The forming operation performed by the wings also constrains the oppositely disposed flanges on the shorter edges of the blank to interlock on the underside of the mandrel whereupon a second forming tool compresses the metal of the blank in the interlocked region to form the vertical seam within the wall of the tin box. During all forming operations the blank is clamped against the upper surface of said mandrel by said mandrel clamping arrangement.
The bodymaker thus forms the walls of the tin box into the desired cross-sectional whereafter the hollow wall section is fed into the round and irregular seamer which seamingly attaches a base provided with a peripheral flange by simultaneously compressing and deforming said peripheral flange and the partial curl provided on one of the edges of the blank together to form a seam. In practice, the bodymaker is responsible for the formation of the hooks on the shorter edges of the blank to facilitate connection of said edges to one another.
The seamer is conventionally juxtaposed with the bodymaker and an end feeder, these two pieces of machinery providing the body of the tin box and its base respectively which are connected together by the seamer. The seamer is also provided with a turret table which intermittently rotates, the intermittency dependent on the rate of production of tin boxes, the duration of the various forming steps throughout the production process, and the rate of infeed of blanks.
This invention is specifically concerned with the provision of an axial displacement mechanism for the turret plate of the seamer which ensures precise angular orientation of said turret plate with respect to the various stations which said table serves, and also precise axial disposition with respect to each of these stations and to the seaming chuck of the seamer.
The turret plates currently in use on seaming machines are generally circular or quadrangular and rotate periodically by approximately 90xc2x0 every rotation and also always in the same direction. Said turret plates are provided with apertures and overlie a turret table which is rigidly secured to a frame which does not rotate. The surface of the turret table is generally smooth over its upper surface such that the hollow tubular portion of a partially complete tin box in contact therewith around one of its perimetral edges can slide unimpeded thereacross as the turret plate rotates above. It will be understood by those skilled in the art that the tubular portion stands vertically on said turret table and it is the free perimetral edge thereof to which a base is to be seamed in the seaming chuck. The turret plate provides support for said tubular base portion around the free perimetral edge thereof thus preventing the tubular portion from falling over as it moves over the turret table.
A base for the tubular portion is supplied by an end feeder adjacent one of the four positions in which the turret table and plate are disposed during stepwise rotation of said turret plate. Said end feeder positions the substantially planar pre-formed base on the turret plate over one of the apertures thereof before the turret plate is rotated to the seaming station. The separation of the turret table which supports the tubular portion of the box and the turret plate is such that the uppermost, free perimetral edge of the tubular portion is marginally lower than the upper surface of the turret plate by which the planar base is supported, and accordingly said uppermost edge of the tubular portion is not in contact with the lower surface of the planar base.
After the turret plate is rotated into position underneath the seaming chuck of a round and irregular seamer, thus causing the tubular portion and base to move also, an actuation mechanism underneath the turret table urges the tubular portion upwardly such that its uppermost edge comes into contact with the planar base and lifts same above the upper surface of the turret plate. In this condition, the upper region of the tubular portion stands proud of the turret plate to allow the seaming chuck to act around the uppermost edge and seam the planar base thereto.
After the seaming operation is completed, the tin box is allowed to drop back onto the turret table, and the turret plate again rotates to a station where either the tin box is filled or removed.
Turret tables are usually rigidly secured to a supporting frame and do not rotate, whereas turret plates are commonly connected to a rotationally driven spindle by means of a taper lock bush. Such connection consists of a frusto-conical member which is disposed in a hollow end of the spindle and which is expanded as a bolt is screwed therethrough. The bush engages the inner walls of the hollow portion of the spindle as it expands and so secures the turret plate thereto. Such means of connection of the turret plate to the spindle allows the turret plate to move with two degrees of freedom (i.e. axially and rotationally), and although the turret plate may be provided with key means to ensure correct angular orientation with respect to the turret table, it is essential to accurately fix the axial separation of the turret table and turret plate because the distance between the turret plate and the seaming chuck must be constant. The relative height of the seaming chuck with respect to the turret table can be altered by raising or lowering said seaming chuck, and therefore different heights of tubular portions to which a base is to be seamed can be accommodated, but precise axial positioning of the turret plate is required to ensure that when the tubular portion is raised, its uppermost perimetral edge stands proud of the upper surface of the turret plate by a uniform amount. It will be appreciated by those skilled in the art that the precise axial positioning of a turret plate secured to a drive shaft by a taper lock bush can be time consuming and prone to human error.
It will also be understood from the above that imprecise angular orientation of the turret plate with respect to the various stations which it serves can result in production inefficiencies, as the entire process must be stopped to correctly align the table. This is a further disadvantage which the invention seeks to overcome.
It is the object of the invention to provide a turret plate axial displacement mechanism which ensures precise axial positioning of said plate with respect to the turret table and seaming chuck, and also to ensure precise angular orientation of said turret plate relative to the turret table.
According to the invention there is provided an axial displacement and locking mechanism for a turret plate rotationally driven by a spindle to which said mechanism is rigidly secured or with which said mechanism in integral, said mechanism allowing for precise adjustment of angular and axial orientation of said turret plate, said mechanism comprising an axially fixed portion and an axially movable portion, said axially fixed portion comprising location means which are received in the movable portion and prevent same from rotating relative to the fixed portion, characterised by screw means which are provided with threads which engage corresponding threads in the axially movable portion such that rotation of the screw means causes the axially movable portion to rise or fall relative to the fixed portion on the location means.
Preferably the screw means abut the fixed portion.
Preferably said screw means also comprises secondary screw means which can be received in a threaded aperture within the fixed portion to lock said axially movable portion at a particular axial displacement relative to said fixed portion.
Preferably the plate is connected to the axially movable portion.
Preferably the axially movable portion comprises an annular bush the centre of which engages with the screw means and which is provided with a plurality of apertures to allow for connection of the plate with bolts or the like.
Preferably the annular bush comprises spacer means which extend the overall height of the annular bush and allow for the connection of a plate at the uppermost extremity thereof.
The axial displacement mechanism described above represents a significant advance of existing turret table/plate mechanisms because not only is the possibility of relative angular rotation between the turret plate, the turret table and the drive shaft precluded, there is provision for infinitesimal axial displacement of said plate without any requirement to support said plate during the adjustment. Previously, it was necessary to insert packing blocks between the table and plate such that the plate was supported by the table during axial displacement of said plate relative to said table. The plate is supported by the screw means which abut the fixed portion of the mechanism or the uppermost end of the drive shaft. Hence axial displacement is rendered simple, quick and effective.
Furthermore, the capability for adding spacer elements into the mechanism construction increases the versatility of the mechanism as a whole and allows for a far greater range of tin box depths to be accommodated on the turret table.
It is to be mentioned that the word xe2x80x9cfixedxe2x80x9d herein means precluded from moving axially of the adjustment mechanism as opposed to being axially movable, except where the contrary is immediately apparent. Indeed the xe2x80x9cfixed portionxe2x80x9d as referred to hereinbefore and after is rotationally driven by virtue of its connection to the spindle.